Conventionally, in optical communications using an optical transmission member such as optical fibers or optical waveguides, an optical module having a light emitting element such as a surface-emitting laser (for example, a VCSEL: Vertical Cavity Surface Emitting Laser) is used. The optical module has an optical receptacle that causes light including communication information emitted from a light emitting element to be incident on an end surface of an optical transmission member.
Some optical modules have a detecting element for monitoring the intensity and amount of light emitted from the light emitting element for the purpose of stabilizing output characteristics of the light emitting element against temperature changes and of adjusting the light output.
For example, in PTL 1 an optical module is disclosed which has a photoelectric conversion device in which a light emitting element and a detecting element are disposed, and an optical receptacle that optically connects the light emitting element and an end surface of an optical transmission member.
FIG. 1 is a cross-sectional view that schematically illustrates the configuration of optical module 10 disclosed in PTL 1. As illustrated in FIG. 1, optical module 10 disclosed in PTL 1 includes photoelectric conversion device 20 and optical receptacle 30 made of resin. Optical receptacle 30 includes: first optical surface 31 that allows light emitted from light emitting element 21 to be incident thereon; second optical surface 32 that emits light that passes through the inside thereof so that the light concentrates at end surface 23 of optical transmission member 22; reflecting surface 33 that reflects the light incident on first optical surface 31 to the side of optical transmission member 22; light separating section 34 that separates the light reflected by reflecting surface 33 into monitoring light Lm directed toward the side of detecting element 24, and signal light Ls directed toward the side of optical transmission member 22; and third optical surface 35 that emits monitoring light Lm toward detecting element 24. Light separating section 34 is formed as one part of an inner face of recess 36 that is formed in optical receptacle 30.
In optical module 10 disclosed in PTL 1, the light emitted from light emitting element 21 and incident on first optical surface 31 is reflected by reflecting surface 33 toward light separating section 34. The light reflected by reflecting surface 33 is separated into signal light Ls and monitoring light Lm by light separating section 34. Monitoring light Lm separated by light separating section 34 is emitted from third optical surface 35 toward a light receiving surface of detecting element 24. On the other hand, signal light Ls separated by light separating section 34 passes through light separating section 34 and is emitted to outside of optical receptacle 30. Signal light Ls is then incident again on optical receptacle 30 from incidence surface 37 that is another part of the inner face of recess 36. Signal light Ls incident on incidence surface 37 is emitted from second optical surface 32 toward end surface 23 of optical transmission member 22.